Spark-plug.



A A. RADTKE. SPARK PLUG.

APPLICATION FILED JUNE 7. 1917.

Patented Jan. 7,1919.

bifiwsses UNITED STATES PATENT OFFICE.

ALBERT L warmer cmcmo, ILLINOIS.

' sranx rnue.

Th allwhomz'tmay concern: Be it known that I, ALBERT A. RADTKE, a citizen of the United States, residing at .the city of Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Spark- Plugs, of which the following is a specification.

My invention relates to ignition devices for internal combustion engines, and -particularly to that form of ignition devices known as spark plugs, in which a spark is caused to jump a gap for the purpose of igniting the explosive mixture. It is well known that when a potential is ressed upon electrodes separated by a spar gap there is a' definite time lag between the impressing of the potential and the'passing of the spark,

' and that in all forms of potential producing devices, such as magnetos, induction coils and spark coils, the potential reduced is of a wave form which rises an falls, and, consequently, the. time lag of the spark is frequently solong that the potential wave" falls below the sparking potential before the discharge takes place.

The object of my invention is to reduce the time lag and facilitate the passage of the spark. I have found that if a side spark or discharge is produced near one of the electrodes, so that the spark gap and the spark .electrodes are subjected to the action which accompanies and results from the side spark, the main or ignition spark is produced much more easily and without the time lag, and that the spark potential may even be reduced to some extent by this means. This secondary discharge or spark is produced by having an isolated point projecting into the proximity of the electrodes. By isolated I mean having no conductive connection with any portion of the electrical circuit,

and likewise having no connection with a condenser connected in or to the circuit.

The principle and construction of my invention are setforth in the accompanying drawing, in which- Figure 1 is a' sectional elevation; Fig. 2 a bottom view, and Fig. 3 a section on line 3-3.

Further describing my invention with reference to the drawings, which show one form of my plug which embodies these features: v1 is the threaded metal shell, which screws into the engine and to which the ground electrode 2 is fastened. The insu- Speciflcation of Letters latent.

Application filed June 7, 1917. Serial No. 178,892.

Patented Jan. 1919.

"later 3, extending through the 'shell is formed with a flanged projection 4 so as to form a sealed jointwiththe shell when held in place by the screw cap 5 and the metal gasket. 6." In the porcelain insulator there 1s formed .a central bore, through which extends the central electrode 7, which is threaded into the terminal cap 8, and

the terminal nut 9. Within the petticoat portion 10 ofthe insulator 3, and engaging therewith, there is secured a coil of wire 11, one end of which 12 is pointed and bent up so as to approach the end of the central electrode 7. I have found that this member should preferably be a conductor, but that an insulator produces the desired result. I have used various forms of construction with success, but prefer to describe my inention in the form here shown.

The operation of the device is as follows: When the potential of :the electrodes is raised or lowered they have a potential consequently higher or lowerthan the coiled wire member 11, and' asa result a discharge takes place between the center electrode-and the point of the coiled wire member, and since thedistanoe of the coiled wire member to the center electrode is small, a comparatively small potential relative to the main spark potential will cause this discharge,

.and this discharge acts on the main spark gap and spark electrodes and facilitates the one of the main electrodes, and a body portion surrounding such main electrode, and in inductive relation thereto.

.2. In a spark plug, thecombination with the usual shelland insulator, of electrodes respectively carried by said parts, and forming a spark gap directly between themselves,

and a metallic member supported by said "projecting toward and disposed adjacent insulator, said member having a portion associated with but insulated from one of a electrode carried by said insulator, axially electrode carried by thereof, a cooperating) t d b (1 er suppor e y sai said shell, and a mem insulator out of contact with'said electrodes,

said member having a portion disposed in inductive relation to said central electrode and a portion projecting toward the same and extending at substantially right angles thereto.

meogeo 4. In a spark plug, the combination with the usual. shell and insulator, of a central electrode carried by said insulator axially thereof, a cooperating electrode carried by said shell, and a wire coil supported by said insulator, said coil surrounding said central electrode, but insulated from both elecand one end of the wire projecting trodes to the end of said central into proximity electrode. v

In Witness-whereof, I have hereunto subscribed my name this 28th day of May, 1917, at Chicago, Illinois.

ALBERT A. RADTKE 

